27
Challenges  VMs have lots of state in memory  Some VMs have soft real-time requirements  E.g. web servers, databases, game servers  May be members of a cluster quorum  Minimize down-time  Performing relocation requires resources  Bound and control resources used

41
Writable Working Set  Set of pages written to by OS/application  Pages that are dirtied must be re-sent  Hot pages E.g. process stacks Top of free page list (works like a stack)  Buffer cache  Network receive / disk buffers